This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Water-soluble derivatives of endohedral metallofullerenes possess unique potential for medicinal applications since the fullerene cage protects the encapsulated metal ion from external chemical attack and metal ion release in the body. Derivatized water-soluble Gd-based metallofullerenes are excellent MRI contrast agents with unusually large proton relaxivities for agents with no direct Gd-OH2 bonding. Phantom and in vivo MRI studies have both shown promising results 1) Study the affect of ionic strength on the aggregation properties of these water-soluble gadofulllerenes. 2) Study the effect of Human Serum Albumin (HSA) and mice serum on the aggregation properties of the gadofullerenes under physiological conditions. 3) Follow the aggregation behaviour of the gadofullerenes in cell cultures and check for the accumulation inside cells, thereby exploring the potential of gadofullerenes as the first intracellular MRI contrast agents.